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8 results on '"Hvidberg, C.S."'

4. Highly temporally resolved response to seasonal surface melt of the Zachariae and 79N outlet glaciers in northeast Greenland

Author

Rathmann, N.M., Hvidberg, C.S., Solgaard, A.M., Grinsted, A., Gudmundsson, G.H., Langen, P.L., Nielsen, K.P., Kusk, A., Rathmann, N.M., Hvidberg, C.S., Solgaard, A.M., Grinsted, A., Gudmundsson, G.H., Langen, P.L., Nielsen, K.P., and Kusk, A.

Abstract

The seasonal response to surface melting of the Northeast Greenland Ice Stream outlets, Zachariae and 79N, is investigated using new highly temporally resolved surface velocity maps for 2016 combined with numerical modeling. The seasonal speedup at 79N of 0.15 km/yr is suggested to be driven by a decrease in effective basal pressure induced by surface melting, whereas for Zachariae its 0.11 km/yr seasonal speedup correlates equally well with the breakup of its large ice mélange. We investigate the influence 76 km long floating tongue at 79N, finding it provides little resistance and that most of it could be lost without impacting the dynamics of the area. Furthermore, we show that reducing the slipperiness along the tongue-wall interfaces produces a velocity change spatially inconsistent with the observed seasonal speedup. Finally, we find that subglacial sticky spots such as bedrock bumps play a negligible role in the large-scale response to a seasonally enhanced basal slipperiness of the region.

Published
2017

5. Evidence for general instability of past climate from a 250-kyr ice-core record

Author

Dansgaard, W., Johnsen, S.J., Clausen, H.B., Dahl-Jensen, D., Gundestrup, N.S., Hammer, C.U., Hvidberg, C.S., Steffensen, J.P., Sveinbjornsdottir, A.E., Jouzel, J., and Bond, G.

Subjects
Climatic changes -- Research, Glacial epoch -- Arctic, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Analysis of an ice core from Greenland indicates that interglacial periods do not normally have as stable a climate as the current Holocene period displays. The stable-isotope record indicates that climate can change drastically within as little as a few decades. This implies that the current climate may not stay stable as pollutants and greenhouse gasses are added. The last interglacial may also have lasted longer than previously thought.

Published
1993

6. Eemian interglacial reconstructed from a Greenland folded ice core

Author

Dahl-Jensen, D., Albert, M.R., Aldahan, A., Azuma, N., Balslev-Clausen, D., Baumgartner, M., Berggren, A.-M., Bigler, M., Binder, T., Blunier, T., Bourgeois, J.C., Brook, E.J., Buchardt, S.L., Buizert, C., Capron, E., Chappellaz, J., Chung, J., Clausen, H.B., Cvijanovic, I., Davies, S. M., Ditlevsen, P., Eicher, O., Fischer, H., Fisher, D.A., Fleet, L.G., Gfeller, G., Gkinis, V., Gogineni, S., Goto-Azuma, K., Grinsted, A., Gudlaugsdottir, H., Guillevic, M., Hansen, S.B., Hansson, M., Hirabayashi, M., Hong, S., Hur, S.D., Huybrechts, P., Hvidberg, C.S., Iizuka, Y., Jenk, T., Johnsen, S.J., Jones, T.R., Jouzel, J., Karlsson, N.B., Kawamura, K., Keegan, K., Kettner, E., Kipfstuhl, S., Kjær, H.A., Koutnik, M., Kuramoto, T., Köhler, P., Laepple, T., Landais, A., Langen, P.L., Larsen, L.B., Leuenberger, D., Leuenberger, M., Leuschen, C., Li, J., Lipenkov, V., Martinerie, P., Maselli, O.J., Masson-Delmotte, V., McConnell, J.R., Miller, H., Mini, O., Miyamoto, A., Montagnat-Rentier, M., Mulvaney, R., Muscheler, R., Orsi, A.J., Paden, J., Panton, C., Pattyn, F., Petit, J.-R., Pol, K., Popp, T., Possnert, G., Prié, F., Prokopiou, M., Quiquet, A., Rasmussen, S.O., Raynaud, D., Ren, J., Reutenauer, C., Ritz, C., Röckmann, T., Rosen, J.L., Rubino, M., Rybak, O., Samyn, D., Sapart, C.J., Schilt, A., Schmidt, A.M.Z., Schwander, J., Schüpbach, S., Seierstad, I., Severinghaus, J.P., Sheldon, S., Simonsen, S.B., Sjolte, J., Solgaard, A.M., Sowers, T., Sperlich, P., Steen-Larsen, H.C., Steffen, K., Steffensen, J.P., Steinhage, D., Stocker, T.F., Stowasser, C., Sturevik, A.S., Sturges, W.T., Sveinbjörnsdottir, A., Svensson, A., Tison, J.-L., Uetake, J., Vallelonga, P., van de Wal, R.S.W., van der Wel, G., Vaughn, B.H., Vinther, B., Waddington, E., Wegner, A., Weikusat, I., White, J.W.C., Wilhelms, F., Winstrup, M., Witrant, E., Wolff, E.W., Xiao, C., Zheng, J., Dahl-Jensen, D., Albert, M.R., Aldahan, A., Azuma, N., Balslev-Clausen, D., Baumgartner, M., Berggren, A.-M., Bigler, M., Binder, T., Blunier, T., Bourgeois, J.C., Brook, E.J., Buchardt, S.L., Buizert, C., Capron, E., Chappellaz, J., Chung, J., Clausen, H.B., Cvijanovic, I., Davies, S. M., Ditlevsen, P., Eicher, O., Fischer, H., Fisher, D.A., Fleet, L.G., Gfeller, G., Gkinis, V., Gogineni, S., Goto-Azuma, K., Grinsted, A., Gudlaugsdottir, H., Guillevic, M., Hansen, S.B., Hansson, M., Hirabayashi, M., Hong, S., Hur, S.D., Huybrechts, P., Hvidberg, C.S., Iizuka, Y., Jenk, T., Johnsen, S.J., Jones, T.R., Jouzel, J., Karlsson, N.B., Kawamura, K., Keegan, K., Kettner, E., Kipfstuhl, S., Kjær, H.A., Koutnik, M., Kuramoto, T., Köhler, P., Laepple, T., Landais, A., Langen, P.L., Larsen, L.B., Leuenberger, D., Leuenberger, M., Leuschen, C., Li, J., Lipenkov, V., Martinerie, P., Maselli, O.J., Masson-Delmotte, V., McConnell, J.R., Miller, H., Mini, O., Miyamoto, A., Montagnat-Rentier, M., Mulvaney, R., Muscheler, R., Orsi, A.J., Paden, J., Panton, C., Pattyn, F., Petit, J.-R., Pol, K., Popp, T., Possnert, G., Prié, F., Prokopiou, M., Quiquet, A., Rasmussen, S.O., Raynaud, D., Ren, J., Reutenauer, C., Ritz, C., Röckmann, T., Rosen, J.L., Rubino, M., Rybak, O., Samyn, D., Sapart, C.J., Schilt, A., Schmidt, A.M.Z., Schwander, J., Schüpbach, S., Seierstad, I., Severinghaus, J.P., Sheldon, S., Simonsen, S.B., Sjolte, J., Solgaard, A.M., Sowers, T., Sperlich, P., Steen-Larsen, H.C., Steffen, K., Steffensen, J.P., Steinhage, D., Stocker, T.F., Stowasser, C., Sturevik, A.S., Sturges, W.T., Sveinbjörnsdottir, A., Svensson, A., Tison, J.-L., Uetake, J., Vallelonga, P., van de Wal, R.S.W., van der Wel, G., Vaughn, B.H., Vinther, B., Waddington, E., Wegner, A., Weikusat, I., White, J.W.C., Wilhelms, F., Winstrup, M., Witrant, E., Wolff, E.W., Xiao, C., and Zheng, J.

Abstract

Efforts to extract a Greenland ice core with a complete record of the Eemian interglacial (130,000 to 115,000 years ago) have until now been unsuccessful. The response of the Greenland ice sheet to the warmer-than-present climate of the Eemian has thus remained unclear. Here we present the new North Greenland Eemian Ice Drilling (‘NEEM’) ice core and show only a modest ice-sheet response to the strong warming in the early Eemian. We reconstructed the Eemian record from folded ice using globally homogeneous parameters known from dated Greenland and Antarctic ice-core records. On the basis of water stable isotopes, NEEM surface temperatures after the onset of the Eemian (126,000 years ago) peaked at 8 ± 4 degrees Celsius above the mean of the past millennium, followed by a gradual cooling that was probably driven by the decreasing summer insolation. Between 128,000 and 122,000 years ago, the thickness of the northwest Greenland ice sheet decreased by 400 ± 250 metres, reaching surface elevations 122,000 years ago of 130 ± 300 metres lower than the present. Extensive surface melt occurred at the NEEM site during the Eemian, a phenomenon witnessed when melt layers formed again at NEEM during the exceptional heat of July 2012. With additional warming, surface melt might become more common in the future.

Published
2013

7. Introduction to the 4th Mars Polar Science and Exploration Conference special issue: Five top questions in Mars polar science

Author

Fishbaugh, K.E., Hvidberg, C.S., Beaty, D., Clifford, S., Fisher, D., Haldemann, A., Head, J.W., Hecht, M., Koutnik, M., Tanaka, K., and Ammann, W.J.

Subjects
*MARS (Planet), *EARTH sciences, *GEOLOGY, *EVENT stratigraphy
Abstract

Abstract: As an introduction to this Icarus special issue for the 4th Mars Polar Science and Exploration Conference, we discuss five key questions in Mars polar science, gleaned from plenary discussions and presentations held at the conference. These questions highlight major unknowns in the field. (1) What are the physical characteristics of the polar layered deposits (PLD), and how are the different geologic units within, beneath, and surrounding the PLD related? (2) How old are the PLD? And what are their glacial, fluvial, depositional and erosional histories? (3) What are the mass and energy budgets of the PLD, and what processes control these budgets on seasonal and longer timescales? (4) What chronology, compositional variability, and record of climatic change is expressed in the stratigraphy of the PLD? (5) How have volatiles and dust been exchanged between polar and non-polar reservoirs? And how has this exchange affected the past and present distribution of surface and subsurface ice? [Copyright &y& Elsevier]

Published
2008
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8. High-resolution record of Northern Hemisphere climate extending into the last interglacial period.

Author

Andersen, K.K., Azuma, N., Barnola, J.-M., Bigler, M., Biscaye, P., Caillon, N., Chappellaz, J., Clausen, H.B., Dahl-Jensen, D., Fischer, H., Flückiger, J., Fritzsche, D., Fujii, Y., Goto-Azuma, K., Grønvold, K., Gundestrup, N.S., Hansson, M., Huber, C., Hvidberg, C.S., and Johnsen, S.J.

Subjects
ICE, CHRONOLOGY, GLACIAL Epoch, ISOTOPES, OXYGEN
Abstract

Two deep ice cores from central Greenland, drilled in the 1990s, have played a key role in climate reconstructions of the Northern Hemisphere, but the oldest sections of the cores were disturbed in chronology owing to ice folding near the bedrock. Here we present an undisturbed climate record from a North Greenland ice core, which extends back to 123,000 years before the present, within the last interglacial period. The oxygen isotopes in the ice imply that climate was stable during the last interglacial period, with temperatures 5°C warmer than today. We find unexpectedly large temperature differences between our new record from northern Greenland and the undisturbed sections of the cores from central Greenland, suggesting that the extent of ice in the Northern Hemisphere modulated the latitudinal temperature gradients in Greenland. This record shows a slow decline in temperatures that marked the initiation of the last glacial period. Our record reveals a hitherto unrecognized warm period initiated by an abrupt climate warming about 115,000 years ago, before glacial conditions were fully developed. This event does not appear to have an immediate Antarctic counterpart, suggesting that the climate see-saw between the hemispheres (which dominated the last glacial period) was not operating at this time. [ABSTRACT FROM AUTHOR]

Published
2004
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